Experimental infections in humans-historical and ethical reflections

Vaccine efficacy and prophylactic treatment of infections are tested best when the vaccinated or treated individual is challenged through deliberate infection with the respective pathogen. However, this trial design calls for particular ethical caution. Awareness of the history of challenge trials is indispensable, including trials that were problematic or even connected to abuse. We briefly introduce historical aspects of experimental infections in humans and the ethical debate around them and give estimates of the numbers of volunteers participating in human experimental infection models. Challenge models can offer a great chance and benefit for the development of medical interventions to fight infectious diseases, but only when they are appropriately controlled and regulated.